Grain sorghum is now booting and we applied initial insecticide sugarcane aphids (SCA) last week. This week we are seeing another aphid – corn-leaf aphid (CLA) in sorghum. Unlike the SCA, this aphid was seeing on the top of the leaves and near the whorl of the plant.
UGA Extension Entomologist Dr. David Buntin says (CLA) normally occur in the whorl leaves but can be found lower down on the plant too. They are not a significant pest unless they build to large numbers, but they do not cause the feeding damage that SCA do. Usually rain and beneficial insects will control them. Our SCA insecticides should kill them.
How do we know exactly when to treat for corn-leaf aphids if they become a problem? Dr. Buntin says, we do not have a definite threshold for corn leaf aphid, so just treat when aphids are numerous and leaves begin to look damaged (or chlorotic, yellowing). If only in 2 spots I would wait and see if they get worse.